JP3832954B2 - Pneumatic radial tire for motorcycles - Google Patents

Description

【００３８】
【表２】

【００３９】
なお、表２中の従来タイヤ１は、図３に示すトレッドパターンを有するものとし、従来タイヤ２は、図４に示すタイプで、主溝と副溝とで構成されており、かつ副溝がジグザグ状に延びて主溝の相互を連結するパターンとした。なお副溝幅は主溝の８０％とし、溝深さは主溝と同じにした。
【００４０】
【発明の効果】
前記実施例からも明らかなように、この発明によれば、シミーの発生を有効に防止するとともに、ウェットグリップ性を高めてなお、傾斜副溝の耐溝底クラック性を十分に高めることができる。
【図面の簡単な説明】
【図１】この発明の実施形態を、複数種類の傾斜副溝とともに示すトレッドパターンの略線展開図である。
【図２】図１のＡ−Ａ線に沿う断面図である。
【図３】従来タイヤを示すトレッドパターンの略線展開図である。
【図４】他の従来タイヤを示す、図１と同様の図である。
【符号の説明】
１ トレッド踏面
２，３ 傾斜主溝
４〜１１ 傾斜副溝
７ａ，７ｂ 副溝部分
８ａ，９ａ，１０ａ，１０ｂ 主要部分[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire for a motorcycle, and more particularly to a tread pattern thereof. In particular, the present invention combines durability and steering stability at a high level.
[0002]
[Prior art]
A belt with a belt layer cord extending substantially in the tread circumferential direction is provided, and an inclined main groove having an acute side inclination angle of 45 ° or more with respect to the tread circumferential direction is extended from the tread center to the tread shoulder region on the tread surface. As a conventional tread pattern of this type of tire having a directional pattern provided, for example, with respect to the inclined main groove, as shown by a schematic development view in FIG. In some cases, the inclined main grooves 51 and 52 that are convexly curved toward the tire rotation direction are provided symmetrically with respect to the tread center C.
[0003]
However, in such a tire, and in the tread pattern, there is a problem that shimmy is likely to occur particularly in the front wheel tire due to the high bending rigidity of the tread in the meridian section of the tire. Further, since the circumferential direction components of the main grooves 51 and 52 are small, there is a problem that wet drainage performance, side slip resistance and the like are low, and high road surface grip force on a wet road surface cannot be exhibited.
[0004]
On the other hand, in the tread tread surface, in addition to the inclined main grooves 51, 52, in addition to providing a circumferential groove that is linearly continuous in the tread circumferential direction, when adjusting the bending rigidity of the tread, Although it is possible to suppress the occurrence of shimmy and improve wet drainage performance, bending at the groove bottom portion of the circumferential groove is related to the belt layer cord extending substantially in the tread circumferential direction. As the drag becomes smaller, there is a disadvantage that the groove bottom crack occurs relatively early.
[0005]
Therefore, as shown in part in FIG. 4, in addition to the inclined main grooves 51 and 52, the tread tread surface is provided with a zigzag circumferential groove 53 that extends continuously in a zigzag shape in the tread circumferential direction, or extends linearly. An inclined sub-groove 54 or 55 that intersects the main grooves 51 and 52 or opens at both ends is provided, or extends between the main grooves 51 and 52 in a straight line without communicating with them. For example, an inclined sub-groove 56 that is inclined at a large angle α exceeding 30 ° with respect to the direction is provided.
[0006]
According to these, because of the presence of the zigzag circumferential groove 53 and the inclined sub-grooves 54, 55, or 56, generally, improvement of wet drainage performance is realized together with suppression of shimmy.
[0007]
[Problems to be solved by the invention]
However, when the zigzag circumferential groove 53 continuous in the tread circumferential direction is provided, it is better than the straight groove, but it is disadvantageous in terms of stability and maneuverability due to excessively low rigidity, and the main grooves 51 and 52 are also disadvantageous. If the inclined sub-grooves 54 and 55 intersecting or opening are provided, the rigidity becomes lower than that of the zigzag circumferential groove 53, which is further disadvantageous for stability and maneuverability.
Moreover, in any of these cases, the occurrence of groove bottom cracks in the circumferential groove 53 and the sub-grooves 54 and 55 cannot be sufficiently suppressed.
[0008]
When the inclined sub-groove 56 having an inclination angle α exceeding 30 ° with respect to the tread circumferential direction is provided, the wet drainage performance is not so improved, and the tread circumferential component of the sub-groove 56 is small. Also, since the tread circumferential length of the groove edge is short, there is a problem that the side slip resistance of the tire cannot be increased as expected.
[0009]
The present invention was made as a result of studying as a subject to solve such problems of the prior art, and the object of the present invention is to prevent the occurrence of shimmy and to provide excellent wetness. Air for motorcycles that has improved drainage performance, increased side-slip resistance, improved handling stability on wet roads, effectively prevented the occurrence of groove bottom cracks, and improved tread durability. In providing radial tires.
[0010]
[Means for Solving the Problems]
A pneumatic radial tire for a motorcycle according to the present invention includes a belt in which a belt layer cord is substantially extended in the tread circumferential direction, and has an acute angle with respect to the tread circumferential direction on the tread tread surface without a circumferential groove continuous in the tread circumferential direction. An inclined main groove having a side inclination angle of 45 ° or more is provided to extend from the tread center or the vicinity thereof to the tread shoulder region, and, for example, between two inclined main grooves on each side of the tread center. , Having a directional pattern formed by extending inclined sub-grooves whose acute-side inclination angle with respect to the circumferential direction of the tread is smaller than those inclined main grooves. In the range of 3-15% of the peripheral length between the tread ends under an unloaded posture filled with 80% of the maximum air pressure. The main portion having at least one of width and depth larger than the other portion is terminated without opening the inclined main groove, and the acute side inclination angle of the main portion with respect to the tread circumferential direction is in the range of 0 to 30 °. And the width of the main portion is narrower than that of the inclined main groove, and the length of the main portion in the circumferential direction of the tread is in the range of 30 to 80% of the pitch of the inclined main groove. The depth of the portion is in the range of 50 to 100% of that of the inclined main groove.
[0011]
Here, the inclined sub-groove can be disposed so as to overlap the tread center. In this case, the inclined sub-groove extends between the two pairs of inclined main grooves communicating with each other at the tread center. Become.
[0012]
Here, the main part of the inclined sub-groove refers to a wide part and a deep part when the sub-groove has at least one of a groove width and a groove depth. When the groove width and the groove depth are both constant, the entire inclined sub-groove becomes the main part.
[0013]
By the way, when each of the sub-groove has a narrow groove width and a deep groove depth part and a wide width and shallow part, the main part is a deep groove part. And when there are multiple wide or deep portions in one sub-groove, these multiple locations are all the main parts of one inclined sub-groove. The length of the main part is their total length.
[0014]
This is almost the same when a plurality of sub-groove portions extend at intervals on a single straight line.
[0015]
In such a pneumatic radial tire, the belt layer cord is extended substantially in the tread circumferential direction by, for example, spiral winding of one or a plurality of cords, thereby achieving high-speed durability and driving on a dry road surface. The stability etc. can be improved, and the slanted main groove has an acute side slope angle of 45 ° or more with respect to the tread circumferential direction, and smooth and quick side drainage is realized. Driving and braking performance can be provided, and further, bending rigidity in the cross section in the width direction can be ensured, and excellent road surface grip force when turning on a dry road surface can be provided.
[0016]
Also, by setting the groove width of the inclined main groove in the range of 3 to 15% of the peripheral length between the tread ends, the tread bending rigidity is appropriately reduced and the contact length / width is appropriately increased. It can realize excellent grip on dry and wet roads, controllability and stability of sliding, and also realize sufficient drainage, and also realize excellent grip on wet roads. Can do. That is, if it is less than 3%, the tread bending rigidity cannot be advantageously reduced, and the drainage cannot be secured sufficiently, so the above grip force, slip control performance, stability and grip performance on wet roads are not possible. Is not enough. On the other hand, if it exceeds 15%, the grip stability on the dry road cannot be sufficiently secured because the rigidity of the tread portion is too low.
[0017]
Further, the inclined sub-groove is finished without opening the main portion of the inclined sub-groove to the inclined main groove, and the acute angle side inclination angle of the main portion with respect to the tread circumferential direction is in a range of 0 to 30 °. In addition to improving the wet drainage performance by comprehensively optimizing the width, depth, etc. of the main part, the arrangement method, dimensions, etc. of the inclined sub-grooves, the tread bending within the meridian section of the tire The groove bottom crack resistance is advantageously improved by securing a moderate rigidity, and the groove edge length effective for the lateral direction input can be sufficiently secured to provide a high side slip resistance. An inclined sub-groove can be arranged at a position particularly effective for lowering the cornering power with respect to the handle shimmy, that is, in a contact area during straight traveling.
[0018]
As a result, it is possible to increase the lateral grip on wet roads, bring about the required rigidity when driving on dry roads, and fully optimize the lightness and stability of handling. Especially in the front tire, the occurrence of shimmy can be effectively suppressed.
[0019]
By the way, when the inclination angle of the main part exceeds 30 °, the drainage performance is lowered, and the lateral grip force on the wet road surface, in other words, the side slip resistance may be lowered.
[0020]
Further, here, by making the groove width of the main portion narrower than that of the inclined main groove, it is possible to effectively ensure steering stability and wear resistance. That is, if the groove width of the main part is wider than that of the inclined main groove, the tread bending rigidity in the meridian section may be reduced more than necessary, and the steering stability may be impaired. The wear resistance may be deteriorated.
[0021]
In addition, by making the length of the tread circumferential direction of the main portion in the range of 30 to 80% of the pitch of the inclined main groove, it is possible to ensure higher wet drainage performance, side slip resistance, etc. Can also be increased sufficiently. That is, when it is less than 30%, it is difficult to sufficiently exert the effect of arranging the inclined sub-groove, and when it exceeds 80%, the bending rigidity in the meridian cross section of the tread becomes too low, and steering stability is reduced. The decline cannot be denied.
[0022]
In addition, in this tire, the depth of the main portion is set to 50 to 100% of that of the inclined main groove, thereby ensuring better wet drainage performance. That is, if it is less than 50%, wet drainage performance tends to be insufficient, and if it exceeds 100%, the tread thickness on the inner periphery side from the groove bottom becomes too thin, and there is a high risk of occurrence of puncture due to nails or the like. Become.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on the drawings.
FIG. 1 is a schematic development view of a tread pattern partially showing an embodiment of the present invention with respect to eight inclined sub-grooves. Normally, all the inclined sub-grooves are positioned symmetrically with respect to the tread center. And repeatedly formed at equal pitches in the tread circumferential direction.
[0024]
As shown in the figure, inclined main grooves 2 and 3 having an acute-side inclination angle β of 45 ° or more with respect to the tread circumferential direction are linearly extended from the tread center C to the tread end E on the tread road surface 1. At the same time, the inclined main grooves 2 and 3 are positioned symmetrically with respect to the tread center C.
[0025]
Here, each of the inclined main grooves 2 and 3 has a peripheral length of 3 to 15 between the tread ends in an unloaded posture in which the tire is assembled to the standard rim and filled with 80% of the maximum air pressure. % Having a groove width in the range of%.
[0026]
The first aspect of the inclined sub-groove formed between the inclined main grooves is positioned so as to overlap the tread center C as shown by 4 in the figure, and ends without opening any of the inclined main grooves. The inclined sub-groove 4 has a constant width and depth over its entire length. Accordingly, the inclined sub-groove 4 has an acute-side inclination angle of 0 ° with respect to the tread circumferential direction and does not have a substantial inclination, and the whole forms a main part.
[0027]
By the way, here, the groove width of the inclined sub-groove 4 is narrower than that of the inclined main grooves 2 and 3, and the length in the tread circumferential direction is 30 to 80 of the arrangement pitch of the inclined main grooves 2 and 3. % And its depth is in the range of 50-100% of that of the inclined main grooves 2,3.
[0028]
Although the inclined sub-groove 4 as described above extends substantially in the same direction as the belt layer cord, the sub-groove 4 is discontinuous with the inclined main grooves 2 and 3, and the discontinuous portion is not present. Since it functions to keep the tread rigidity sufficiently high against bending deformation in the meridian section of the tire, the occurrence of cracks in the bottom of the sub-groove 4 is sufficiently prevented. In addition, the sub-groove 4 extending in the tread circumferential direction can provide particularly excellent wet drainage performance, and the groove edge can provide a high side slip effect on the wet road surface.
[0029]
In the figure, 5 and 6 indicate the second and third aspects of the inclined sub-groove, respectively. These sub-grooves 5 and 6 extend at the respective sides of the tread center C so as to be inclined in the same direction as the inclined main grooves 2 and 3, and have an inclination angle θ on the acute angle side with respect to the tread circumferential direction. ₁ and θ ₂ are in the range of 0 to 30 °.
[0030]
In this case, the circumferential length of the tread is longer than the minor groove 6 in the minor groove 5, but any of those circumferential lengths sufficiently satisfies the requirements described above. The same applies to the groove width and the groove depth.
[0031]
The inclined sub-groove 7 of the fourth aspect is composed of two sub-groove portions 7a and 7b that are spaced on the same straight line. Here, the sub-groove portions 7a and 7b are Both form the main part of the sub-groove 7. Therefore, the tread circumferential length of the main portion here means a tread circumferential direction component of the total length of the sub-groove portions 7a and 7b.
[0032]
The inclined sub-groove 8 of the fifth aspect extends toward the tread end side substantially parallel to the main groove 3 at the end of the wide main portion 8a inclined in the same direction as the inclined main groove 3 on the tire rotation direction side. The narrow bent portion 8b is provided, and here, the main portion 8a is assumed to satisfy the above requirements.
[0033]
As shown in FIG. 1, the inclined sub-groove 9 according to the sixth aspect has a large groove width at each end of the main portion 9a having a large groove width and a deep groove depth as shown in FIG. 3, straight extension portions 9b and 9c having a narrow groove width and a shallow depth are formed. Again, the main part 9a shall satisfy all of the above-mentioned requirements.
[0034]
In the inclined sub-groove 10 of the seventh aspect, the main portions 10a and 10b formed in substantially the same manner as the sub-groove parts 7a and 7b of the inclined sub-groove 7 of the fourth aspect are mutually connected with a narrow intermediate portion 10c. Here, the intermediate portion 10c does not become a main portion.
The inclined sub-groove 11 of the eighth aspect has an inclined direction opposite to the main groove 3.
[0035]
As described above, various aspects of the inclined sub-groove have been described. By forming at least one inclined sub-groove in these aspects regularly on the tread surface 1, as described above, high wet drainage and side slip In addition to providing drag, it is possible to greatly improve the tread durability by preventing the occurrence of cracks in the bottom of the sub-groove.
[0036]
【Example】
The size is 120 / 70ZR17, the main groove has a rug-based tread pattern that is continuous from side to side, the acute side inclination angle β with respect to the tread circumferential direction of the inclined main grooves 2 and 3 is 60 °, and the inclined main groove and Each of the inclined sub-grooves has the dimensional specifications shown in Table 1 and is mounted on the front wheel of the motorcycle to run and feel controllability, stability, wet road surface grip, etc. As a result of evaluation, the groove bottom crack resistance of the secondary groove was determined by a drum test, and the results were as shown in Table 2.
[0037]
[Table 1]

[0038]
[Table 2]

[0039]
The conventional tire 1 in Table 2 has the tread pattern shown in FIG. 3, and the conventional tire 2 is of the type shown in FIG. 4 and is composed of a main groove and a sub groove, and the sub groove has The pattern extends in a zigzag shape and connects the main grooves to each other. The sub-groove width was 80% of the main groove, and the groove depth was the same as that of the main groove.
[0040]
【The invention's effect】
As is clear from the above-described embodiments, according to the present invention, it is possible to effectively prevent the occurrence of shimmy and sufficiently improve the resistance to cracks at the bottom of the inclined sub-groove while improving the wet grip property. .
[Brief description of the drawings]
FIG. 1 is a schematic line development view of a tread pattern showing an embodiment of the present invention together with a plurality of types of inclined sub-grooves.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a schematic development view of a tread pattern showing a conventional tire.
FIG. 4 is a view similar to FIG. 1, showing another conventional tire.
[Explanation of symbols]
1 Tread tread 2, 3 Inclined main grooves 4-11 Inclined subgrooves 7a, 7b Subgroove parts 8a, 9a, 10a, 10b Main parts

Claims (1)

The belt has a belt in which the belt layer cord is substantially extended in the tread circumferential direction, and there is no circumferential groove continuous in the tread circumferential direction on the tread surface. The groove is provided to extend from the tread center or the vicinity thereof to the tread shoulder region, and an inclined sub-groove is provided between the inclined main grooves so that the acute side inclination angle with respect to the tread circumferential direction is smaller than the inclined main groove. A pneumatic radial tire for a motorcycle having a directional pattern with a groove width of an inclined main groove under a no-load posture in which the tire is assembled to a standard rim and filled with an air pressure of 80% of the maximum air pressure. The peripheral portion between the tread ends of each of the main treads is in the range of 3 to 15%, and at least one of the width and the depth of the inclined minor groove is larger than the other portion The main groove is terminated without opening, and the acute angle of the main portion with respect to the tread circumferential direction is set in a range of 0 to 30 °, and the groove width of the main portion is made narrower than that of the inclined main groove. Two-wheeled vehicle pneumatic in which the length of the tread circumferential direction is in the range of 30 to 80% of the pitch of the inclined main groove and the depth of the main part is in the range of 50 to 100% of that of the inclined main groove Radial tire.

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